The United States and Russia reached a breakthrough deal early on Saturday to try to restore peace in Syria, but air strikes hours later added to rebels' doubts that any ceasefire could hold, Reuters report.

The todays agreement of Kerry and Lavrov promised a nationwide truce from sundown on Monday, improved access for humanitarian aid and joint military targeting of hardline Islamist groups. Also key aim was declared to stop killing civilians by Assad aviation.

But hours later, jets bombed a marketplace in rebel-held Idlib in northwestern Syria, killing at least 25 people and wounding dozens, according to locals and rescue workers who said they believed the planes to be Russian. Idlib province has endured escalating strikes by Russian jets in recent months. According to international aid workers and residents, Putin's forces destroyed medical and private infrastructure across rebel-held territory.

Aleppo was also hit from the air and fighting continued on the ground. The army attacked rebel-held areas, both sides said, pushing to maximize gains before the ceasefire deadline.

Britain-based Syrian Observatory for Human Rights also informed about ten people killed by barrel bombs dropped by Syrian or Russian helicopters on the rebel-held east of the city, and jets bombed rebel-held towns in the northern countryside along insurgent supply routes. In their turn insurgents said they were planning a counter-offensive.

Local media already published video from the scene in Idlib. Residents assure journalists, that they were bombed by Russians.

Rebel spokesman Captain Abdul Salam Abdul Razak said they were studying the peace deal but feared it merely gave the Syrian army a chance to gather forces and pour more Iranian-backed militias into Aleppo.

President Bashar al Assad's government made no comment on the peace deal. Syria's mainstream political opposition High Negotiations Committee (HNC), said it had not received a copy of the deal and would only react after consulting members.